Multi-hull boat

ABSTRACT

A multi-hull boat  50  comprising a pair of side by side hulls  21,  and a wingdeck  22  extending between the hulls  21,  wherein the hulls  21  include inner topsides  23  which are adapted to inhibit the hulls  21  from pitching.

FIELD OF THE INVENTION

The present invention relates generally to boats and in particular, to multi-hull boats.

Although the invention will be described with particular reference to power catamarans, it will be appreciated that the invention may be incorporated into other types of multi-hull boats.

BRIEF DISCUSSION OF THE PRIOR ART

A catamaran is a type of boat which has two side by side hulls which are joined together by a wingdeck. The portion of the side of each hull which faces the other hull and which is located above the waterline is referred to as the inner topside of the hull. The inner topsides of the hulls together with the underside of the wingdeck define a hollow region or tunnel.

There are two main types of catamarans: sailing catamarans and power catamarans. Sailing catamarans are primarily wind-powered and include one or more sails for catching the wind. In contrast to sailing catamarans, power catamarans are usually primarily powered by an engine.

When a power catamaran is driven into head seas so that the waves and the catamaran are travelling in opposite directions, the waves tend to slam up against the underside of the wingdeck. This is undesirable because it can make it uncomfortable for those who are onboard the catamaran and can damage the wingdeck of the catamaran. This problem sometimes occurs because there is inadequate tunnel volume or clearance between the wingdeck and the water to accommodate the waves which pass between the hulls. Inadequate clearance between the wingdeck and the water is usually a result of the hulls of the catamaran being heavier or having a greater loading than was originally intended by the designer of the catamaran. If the strength of the wingdeck is increased so that the wingdeck is able to withstand greater slamming loads, and the overall weight of the catamaran is increased as a consequence of the strengthening, the problem can become even worse.

In some cases it is a lack of reserve buoyancy or overloading in the bows that will cause a catamaran to pitch more than it should and therefore drive the wingdeck down into the waves and cause slamming against the wingdeck. There have been cases with some very fine-bowed power catamarans of people onboard being thrown up so violently by wingdeck slamming that they have hit their heads on a cabin ceiling. Although this is an example of an extreme case of lack of reserve buoyancy in combination with low wingdeck clearance, it does illustrate the forces that can be generated.

Tunnel volume is also critical in allowing the water to dissipate either before or after it strikes the wingdeck, therefore narrower catamarans require a higher wingdeck clearance than wider catamarans. Planing power catamarans do create aerodynamic lift at higher speeds, which softens the ride, however when conditions cause them to come off the plane they are vulnerable to heavy slamming, particularly as many of them have very little or no wingdeck clearance when at rest.

At speeds exceeding approximately 15 knots, displaning or high-speed displacement power catamarans do create some lift from the wingdeck. When designing this type of power catamaran it is usually considered more important to reduce slamming by raising the wingdeck rather than lowering it to create lift, as it is desirable for the catamaran to have seakeeping across a range of speeds. Seakeeping is the ability of a vessel to navigate safely at sea for prolonged periods during stormy weather. Whilst the noise and dramatically increased structural loads are the obvious effects of low wingdeck clearance and tunnel volume, there are some other less obvious effects which slow the vessel and decrease fuel efficiency.

The first of these effects comes from a wave which is caused by the inner sides of the hulls. The waves caused by each hull meet in the middle of the wingdeck as depicted in FIG. 1, and hit the underside of the wingdeck near the transom of the vessel. This causes drag by increasing the wetted surface of the vessel, and sometimes causes a kick in the stern if there is a small slam. The resultant drag slows the vessel or places a greater load on the engines of the vessel which results in increased fuel consumption. This effect can be caused by either the shape of the hulls or by the hulls having too narrow a beam which causes the pressure waves created by the bow sections to meet too early under the wingdeck rather than aft of the boat.

The second effect arises in a following sea where the waves approach the stern of the boat and when the wingdeck is pressed down by the buoyancy of the stern and the forward momentum of the vessel. The vessel will literally surf or run on the wingdeck, which has a benefit in that it decreases the chance of broaching or burying the bows by the lift that the wingdeck creates. Unfortunately, it has the disadvantage of increasing the wetted surface of the vessel dramatically and therefore slowing the vessel, making the vessel more vulnerable to a second wave pooping it (i.e., breaking over its stern). It also increases the fuel consumption of the vessel as more power is needed to overcome the wetted surface.

Referring to FIG. 2, the third and probably least recognised effect is jets or squirts of water driving up at an angle from the inner sides of the hulls and hitting the forward wingdeck panels about a third of the way from the centreline of the vessel to each hull. Whilst these do not add to the wetted surface dramatically, they are very noisy and, if they strike a relatively weak area of the wingdeck, they can damage the wingdeck due to the localised nature of the force which they exert on the wingdeck. Most power catamaran designers have been well aware of these problems and a number of different approaches have been used to solve them.

The first and obvious solution is to increase the wingdeck clearance. Most designers are constantly working on this issue. Unfortunately, like all design features, there is a different “balanced” wingdeck clearance which is practical for different size vessels. If the wingdeck clearance of a particular vessel is higher than the balanced clearance for that vessel, the vessel will look silly, the accommodation which is available on the vessel will be greatly reduced, or the vessel will have too much windage and will consequently be difficult to manage in a cross wind. Although raising the wingdeck reduces the lift which is created at speeds over 15 knots, it is arguable that the small trade off in top speed is balanced by the ability to maintain a high cruising speed in rough conditions.

The second approach which has been used is to start the wingdeck further aft. This is a design feature which has been carried over from sailing catamarans which arguably defines the difference between a converted sailing catamaran and a true power catamaran. Most power catamaran designers who use the high-speed displacement or displaning type hull have moved across from designing sailing catamarans. It is understandable that such designers tend to design power catamarans which have features which they are familiar with, like the look of, and understand. However, at a speed of approximately 15 knots, sailing catamarans and power catamarans separate in their evolution in the same way as did monohull powerboats when they developed distinct paths of displacement and planing types. Whilst the mathematical distinction between displacement and planing hulls is much harder to define in power catamarans, the requirements for seakeeping are not.

Higher bows with their increased windage have a detrimental effect on the windward ability of a sailing cat as the windage pushes the bows to leeward. This however is not a problem with power cats as they have no requirement to work to windward and their power to weight ratio is constant. Also, high bows increase reserve buoyancy and create a drier deck.

Raked bows such as the bow depicted in FIG. 3, reduce the waterline length of a sailing catamaran, and therefore decrease the hull beam to length ratio for a given overall length. Whilst it is always advantageous to maintain as high a hull beam to length ratio as possible, it is less critical in a power catamaran where the power is constant and lift can be created, reducing resistance and wetted surface. Raked bows on a power catamaran provide a better distribution of reserve buoyancy which lifts the wingdeck over waves and reduces slamming.

Sailing catamarans tend to have their bows depressed by the drive of the sails. In particular, the leeward bow of sailing catamarans tends to be depressed. Therefore, keeping the wingdeck entrance further aft as depicted in FIG. 4 makes more sense as the sails often drive the wingdeck down into the water.

At speeds over 15 knots, power catamarans behave in the opposite manner to sailing catamarans, with lift created by both the hull sections and by air being funnelled through the tunnel. Starting the wingdeck entry further aft on a power catamaran will often make the wingdeck entry angle considerably steeper. This will lead to a more severe slam when it does occur and a far more dramatic slowing of the vessel as not only is the wetted surface of the vessel increased, but the vessel will also be required to climb over the wave rather than slide over it.

Other disadvantages to starting the wingdeck further aft on a power catamaran are reduced torsional rigidity and increased wetness as the spray off the bows is compressed between the hulls and blown up between them on to the deck. This spray can be so strong that it can blow trampolines of the wingdeck out at higher speeds besides making the foredeck a very wet place to be.

A third approach has been to place a V-pod or nacelle in between the hulls to increase the reserve buoyancy of the vessel and to break up the solid water, and therefore reduce slamming. The V-pods or nacelles which were originally used were either enlarged stringers as depicted in FIG. 5, or almost a wide shallow third hull as depicted in FIG. 6. Although the stringer types break up the water reasonably well and stiffen the panels of the wingdeck, they do not provide much reserve buoyancy. The wide shallow type were not much good for anything as they just filled the tunnel volume up and provided more flat panels for water to slam against.

In the last few years, the design of the V-pods has been influenced by the wave piercer style, with either a deep third hull type under the forward sections as depicted in FIG. 7 and/or radiused arches further aft. Whilst these go some way to breaking the water up and increasing the buoyancy of the vessel, they often negate the benefits by funnelling the water into the now two smaller tunnels located on either side of the third hull and increasing the velocity of the water when it finally hits the wingdeck panels. Also, because of the surface area inside the tunnel when water is compressed, the wetted surface area of the vessel increases. This slows the vessel and increases the power required to maintain the speed of the vessel.

Referring to FIG. 8, if the wingdeck to inner topsides is too radiused and does not include a V-pod, narrow power catamarans sometimes exhibit rolling characteristics more like a monohull than a catamaran.

Wave piercers have been recognised as better boats at punching into a sea than catamarans because the large nacelle of such boats provides reserve buoyancy. Unfortunately, because of the lack of reserve buoyancy in their small outer bows, wave piercers have a strange corkscrew motion in a quarter following sea and therefore an inclination to suffer wave slap on the outer sections of the nacelle, which can be both noisy and damaging.

It would be desirable to improve the rough water ride of power catamarans. It would also be desirable to reduce the potential for structural damage to power catamarans which is caused by slamming loads. Moreover, it would be desirable to increase the fuel efficiency of power catamarans by minimising their wetted surfaces and therefore drag in all conditions.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome, or at least ameliorate, one or more of the deficiencies of the prior art mentioned above, or to provide the consumer with a useful or commercial choice.

Other objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying illustrations, wherein, by way of illustration and example, a preferred embodiment of the present invention is disclosed.

According to a broad aspect of the present invention there is provided a multi-hull boat comprising a pair of side by side hulls, and a wingdeck extending between the hulls, wherein the hulls include inner topsides which are adapted to inhibit the hulls from pitching.

The inventor has found that adapting the inner topsides to inhibit the hulls from pitching improves the rough water ride of multi-hull boats and inhibits waves from slamming into the wingdeck. Inhibiting waves from slamming against the wingdeck reduces the potential for structural damage to the wingdeck. It also assists in minimising the wetted surfaces and therefore the drag of multi-hull boats in various conditions.

Preferably, the multi-hull boat is a catamaran. In a particular preferred form, the multi-hull boat is a power catamaran.

Preferably, the wingdeck extends from the bows of the hulls to the stern of the hulls.

Preferably, the inner topsides are curved at a location which is adjacent the bows of the hulls.

Preferably, each inner topside includes at least one chine, and at least one inclined surface which is inclined towards the other inner topside. The chines and the inclined surfaces are able to inhibit pitching of the hulls in rough water which inturn inhibits waves from slamming into the wingdeck. In particular, the chines and the inclined surfaces are able to cushion the descent of the boat into a wave and to deflect the wave so that the wave is inhibited from slamming against the wingdeck. The chines and the inclined surfaces also increase the reserve buoyancy of the boat.

In a first preferred form, each of the inner topsides includes a lower chine, an upper chine, a lower inclined surface extending between the lower chine and the upper chine, and an upper inclined surface extending upwardly from the upper chine. In another preferred form, each of the inner topsides includes a lower chine, a middle chine, an upper chine, a lower inclined surface extending between the lower chine and the middle chine, a middle inclined surface extending between the middle chine and the upper chine, and an upper inclined surface extending upwardly from the upper chine.

The chines may extend only partway along the inner topsides. For example, the chines may extend partway along the inner topsides from the bows of the hulls.

In a preferred form, the chines and the inclined surfaces merge with the bows of the hulls.

It is preferred that the chines curve upwardly at a location which is adjacent the bows of the hulls.

The chines preferably have a maximum of width of 5 mm to 500 mm. In a particular preferred form, the chines have a maximum width of 70 mm to 150 mm.

The inclined surfaces of the inner topsides are preferably inclined at an angle of 30° to 60° relative to the vertical. In a particular preferred form, the inclined surfaces are inclined at an angle of 45° relative to the vertical.

The inclined surfaces preferably have a minimum vertical height of 50 mm to 1000 mm. In a particular preferred form, the inclined surfaces have a minimum vertical height of 300 mm.

Preferably, the wingdeck is adapted to inhibit waves from slamming against it. Preferably, an underside of the wingdeck includes at least one protrusion which is adapted to inhibit waves from slamming against the wingdeck. In one particular preferred form, the underside of the wingdeck has two protrusions. In another particular preferred form, the underside of the wingdeck has three protrusions.

Each of the protrusions is preferably at least generally V-shaped and has a pair of diverging sides, and each side preferably includes at least one chine and at least one inclined surface. The chines and inclined surfaces of the protrusions are able to deflect waves so that the waves are inhibited from slamming against the wingdeck.

The inclined surfaces of the protrusions are preferably inclined at an angle of 30° to 80° relative to the vertical. In a particular preferred form, the inclined surfaces are inclined at an angle of 60° relative to the vertical.

The protrusions may extend only partway along the wingdeck.

Preferably, at least one protrusion is located towards the front of the wingdeck.

The hulls of the multi-hull boat preferably have raked bows.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying illustrations, in which:

FIG. 1 is a cross-sectional end elevation of the hulls and wingdeck of a prior art catamaran which depicts the bow waves of the vessel meeting in the tunnel between the hulls and beneath the wingdeck and causing drag on the wingdeck;

FIG. 2 is a cross-sectional end elevation of the hulls and wingdeck of a prior art catamaran which depicts water jets slamming against the wingdeck which extends between the hulls;

FIG. 3 is a side elevation of a raked bow and cross-sectional side elevation of a wingdeck of a prior art power catamaran;

FIG. 4 is a side elevation of a plumb bow and a cross-sectional side elevation of a wingdeck of a prior art sailing catamaran;

FIG. 5 is a cross-sectional end elevation of the hulls and wingdeck of a prior art catamaran which includes a plurality of enlarged stringers on the underside of the wingdeck;

FIG. 6 is a cross-sectional end elevation of the hulls and wingdeck of a prior art catamaran which includes a wide shallow third hull on the underside of the wingdeck;

FIG. 7 is a cross-sectional end elevation of the hulls and wingdeck of a prior art catamaran which includes a deep third hull on the underside of the wingdeck;

FIG. 8 is a cross-sectional end elevation of the hulls and wingdeck of a prior art catamaran which includes a radiused portion extending along the wingdeck and the inner topsides of the hulls;

FIG. 9 is a cross-sectional end elevation of a lower portion of a power catamaran according to a first preferred embodiment of the present invention;

FIG. 10 is a perspective view of a lower portion of a power catamaran according to a second preferred embodiment of the present invention;

FIG. 11 is a front elevation of a lower portion of the power catamaran according to the second preferred embodiment of the present invention; and

FIG. 12 is a front elevation of a lower portion of a power catamaran according to a third preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATIONS

Referring to FIG. 9, a lower portion 20 of a power catamaran according to a first preferred embodiment of the present invention includes a pair of side by side hulls 21, and a wingdeck 22 which extends between the hulls 21. Each hull 21 has an inner topside 23 which is the portion of the hull 21 which is located above the waterline of the hull 21 and which faces the other hull 21. Each inner topside 23 includes a lower stepped chine 24, an upper stepped chine 25, a lower inclined surface 26 which extends between the lower stepped chine 24 and the upper stepped chine 25, and an upper inclined surface 27 which extends from the upper stepped chine 25 to an underside 28 of the wingdeck 22. The lower inclined surface 26 and the upper inclined surface 27 of each inner topside 23 are inclined towards the other inner topside 23 at an angle of 450 relative to the vertical.

The underside 28 of the wingdeck 22 includes a horizontal surface 29, and a pair of generally V-shaped longitudinally-extending protrusions 30 which extend downwardly from the horizontal surface 29 and which are spaced apart from each other and from the inner topsides 23. Each protrusion 30 has a pair of diverging sides 31. Each side 31 includes a lower inclined surface 32, an upper inclined surface 33, and a stepped chine 34 which separates the lower inclined surface 32 from the upper inclined surface 33. The lower inclined surface 32 and the upper inclined surface 33 of each side 31 are inclined by approximately 60° relative to the vertical.

Each hull 21 also includes a keel 35.

The various twin arrows depicted in FIG. 9 represent the flow of water over the various inclined surfaces and chines of the hulls 21 and the wingdeck 22 when the hulls 21 move over waves. The inclined surfaces 26, 27 in combination with the chines 24, 25 of the inner topsides 23 create lift and slow the vertical motion of the hulls 21 relative to the waves by turning the waves downwards and into a spray or vapour so as to inhibit a solid body of water slamming against the underside 28 of the wingdeck 22. Turning the waves into a spray or vapour is advantageous because the vessel is subjected to less drag when water spray or vapour instead of a solid body of water contacts the hulls 21 and the wingdeck 22. This is because water spray and water vapour have lubricating qualities and because contacting the hulls 21 or the wingdeck 22 with water spray or vapour rather than a solid body of water is equivalent to reducing the wetted surface area of the catamaran.

The chines 24, 25 also increase the buoyancy of the hulls 21. The buoyancy of the hulls 21 can be varied by altering the width and position of the chines 24, 25. The entry angle of the chines 24, 25 provides additional lift in following seas and prevents the bows of the hulls 21 from burying and the wingdeck 22 from driving down into waves.

The multiple inclined surfaces and chines of each hull 21 provide the vessel with multiple stages of dampening.

The protrusions 30 are preferably discontinuous and are preferably positioned so that they are best able to deflect solid water and strengthen the wingdeck 22. Similarly to the inclined surfaces 26, 27 and chines 24, 25 of the inner topsides 23, the inclined surfaces 32, 33 and chines 34 of the protrusions 30 increase the reserve buoyancy of the vessel, and also provide lift and reduce the wetted surface area of the vessel so that the vessel is subjected to less drag.

By reducing the wetted surface area and drag of the vessel, the inner topsides 23 and protrusions 30 are able to reduce the fuel consumption of the vessel.

Other benefits of the topsides 23 and protrusions 30 is that the panels which form the inner topsides 23 and the wingdeck 22 are smaller and stiffer than they would otherwise be, and that the interior volume and torsional rigidity of the vessel is increased.

A lower portion 50 of a power catamaran according to a second preferred embodiment of the present is depicted in FIGS. 10 and 11. For convenience, features of the lower portion 50 which are the same as or which are similar to features of the lower portion 20 are referenced using the same reference numerals.

With reference to FIGS. 10 and 11, the inner topside 23 of each hull 21 is curved at a location which is adjacent to a bow 51 of the hull 21 such that the inner topside 23 merges in a gradual manner with the bow 51. The wingdeck 22 extends the length of the hulls 21. The chines 24, 25 of the inner topsides 23 and the surface 29 of the wingdeck 22 curve upwardly at a location which is adjacent to the bows 51. The hulls 21 have a waterline which is indicated by the dotted line 52 in FIG. 11.

There is a vertical distance of approximately 800 mm between the lowest part of the surface 29 and the waterline 52. The vertical distance between the lowest part of the surface 29 and the lowest part of the upper chine 25 is approximately 300 mm, and the vertical distance between the lowest part of the upper chine 25 and the lowest part of the lower chine 24 is also approximately 300 mm.

The lower chine 24 and the upper chine 25 taper towards the bows 51 until they merge with the bows 51. The widest part of the lower chine 24 is approximately 150 mm wide, and the widest part of the upper chine 25 is approximately 100 mm wide.

The lower inclined surface 26 and the upper inclined surface 27 of each inner topside 23 are inclined towards the other inner topside 23 such that the maximum angle of inclination of the lower inclined surface 26 and the upper inclined surface 27 relative to the vertical is 45°.

The protrusions 30 are located towards the front of the wingdeck 22. At a location which is adjacent the front of the wingdeck 22, the protrusions 30 curve upwardly and merge with the surface 29 such that the chines 34 are tapered. The length of each protrusion 30 is approximately equal to a third of the total length of the vessel. The lower inclined surface 32 and the upper inclined surface 33 of each side 31 of each protrusion 30 is inclined by approximately 60° relative to the vertical.

The underside 28 of the wingdeck 22 also has a generally V-shaped protrusion 53 which extends from the rear of the wingdeck 22 and terminates adjacent the rear ends of the protrusions 30. The protrusion 53 has a pair of diverging sides 54 that each include a lower inclined surface 55, an upper inclined surface 56, and an upper chine 57 which separates the lower inclined surface 55 from the upper inclined surface 56. The lower inclined surfaces 55 of the sides extend from a lower chine 58. The lower inclined surface 55 and the upper inclined surface 56 of each side 54 are inclined by approximately 60° relative to the vertical, and the sides 54 taper towards each other at the front end of the protrusion 53.

A lower portion 60 of a power catamaran according to a third preferred embodiment of the present is depicted in FIGS. 12. The lower portion 60 is very similar to the lower portion 50. Therefore, for convenience, features of the lower portion 60 which are the same as or which are similar to features of the lower portion 50 are referenced using the same reference numerals.

The main difference between the lower portion 60 and the lower portion 50 is that each of the inner topsides 23 of the lower portion 60 also has a middle inclined surface 61 and a middle stepped chine 62 to provide the lower portion 60 with greater clearance between the wingdeck 22 and the waterline 52. The middle chine 62 is located between the middle inclined surface 61 and the lower inclined surface 26. The middle chine 62 tapers towards the bow 51 of the hull 21 along which it extends until the chine 62 merges with the bow 51. The widest part of the lower chine 24 is approximately 150 mm wide, the widest part of the middle chine 62 is approximately 100 mm wide, and the widest part of the upper chine 25 is approximately 70 mm wide. The middle chine 62 of each hull 21 curves upwardly at a location which is adjacent to the bow 51 of the hull 21.

The lower surface 26, middle surface 61 and the upper surface 27 of each inner topside 23 are inclined towards the other inner topside 23 such that the maximum angle of inclination of the lower surface 26, middle surface 61 and the upper surface 27 relative to the vertical is 45°.

There is a vertical distance of approximately 1,100 mm between the lowest part of the surface 29 and the waterline 52. The vertical distance between the lowest part of the surface 29 and the lowest part of the upper chine 25 is approximately 300 mm. The vertical distance between the lowest part of the upper chine 25 and the lowest part of the middle chine 62 is approximately 300 mm. The vertical distance between the lowest part of the middle chine 62 and the lowest part of the lower chine 24 is approximately 300 mm.

Throughout the specification and the claims, unless the context requires otherwise, the term “comprise”, or variations such as “comprises” or “comprising”, will be understood to apply the inclusion of the stated integer or group of integers but not the exclusion of any other integer or group of integers.

Throughout the specification and claims, unless the context requires otherwise, the term “substantially” or “about” will be understood to not be limited to the value for the range qualified by the terms.

It will be appreciated by those skilled in the art that variations and modifications to the invention described herein will be apparent without departing from the spirit and scope thereof. The variations and modifications as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth.

It will be clearly understood that, if a prior art publication is referred to herein, that reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country. 

1. A multi-hull boat comprising a pair of side by side hulls, and a wingdeck extending between the hulls, wherein the hulls include inner topsides which are adapted to inhibit the hulls from pitching.
 2. The multi-hull boat defined by claim 1, wherein the multi-hull boat is a catamaran.
 3. The multi-hull boat defined by claim 1, wherein the inner topsides are curved at a location which is adjacent the bows of the hulls.
 4. The multi-hull boat by claim 1, wherein each inner topside includes at least one chine, and at least one inclined surface which is inclined towards the other inner topside.
 5. The multi-hull boat defined by claim 4, wherein the chines extend partway along the inner topsides.
 6. The multi-hull boat defined by claim 4, wherein the chines and the inclined surfaces merge with the bows of the hulls.
 7. The multi-hull boat defined by claim 4, wherein the chines curve upwardly at a location which is adjacent the bows of the hulls.
 8. The multi-hull boat defined by claim 4, wherein the chines have a maximum width of 5 mm to 500 mm.
 9. The multi-hull boat defined by claim 4, wherein the chines have a maximum width of 70 mm to 150 mm.
 10. The multi-hull boat defined by claim 4, wherein the inclined surfaces are inclined at an angle of 30° to 60° relative to the vertical.
 11. The multi-hull boat defined by claim 4, wherein the inclined surfaces are inclined at an angle of 45° relative to the vertical.
 12. The multi-hull boat defined by claim 4, wherein the inclined surfaces have a minimum vertical height of 50 mm to 1000 mm.
 13. The multi-hull boat defined by claim 4, wherein the inclined surfaces have a minimum vertical height of 300 m.
 14. The multi-hull boat defined by claim 1, wherein an underside of the wingdeck includes at least one protrusion which is adapted to inhibit waves from slamming against the wingdeck.
 15. The multi-hull boat defined by claim 14, wherein each of the protrusions is at least generally V-shaped.
 16. The multi-hull boat defined by claim 15, wherein each of the protrusions includes a pair of diverging sides, wherein each of the diverging sides includes at least one chine and at least one inclined surface.
 17. The multi-hull boat defined by claim 16, wherein the inclined surfaces of the protrusions are inclined at an angle of 30° to 80° relative to the vertical.
 18. The multi-hull boat defined by claim 17, wherein the inclined surfaces of the protrusions are inclined at an angle of 60° relative to the vertical.
 19. The multi-hull boat defined by claim 14, wherein the protrusions extend only partway along the wingdeck. 